Relational Memory Is Evident in Eye Movement Behavior despite the Use of Subliminal Testing Methods.

Nickel AE, Henke K, Hannula DE - PLoS ONE (2015)

Bottom Line:
While it is generally agreed that perception can occur without awareness, there continues to be debate about the type of representational content that is accessible when awareness is minimized or eliminated.Eye movements were recorded and recognition memory responses were made.The reported outcomes indicate that memory for studied relationships can be expressed in eye movement behavior without awareness.

Affiliation: Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States of America.

ABSTRACTWhile it is generally agreed that perception can occur without awareness, there continues to be debate about the type of representational content that is accessible when awareness is minimized or eliminated. Most investigations that have addressed this issue evaluate access to well-learned representations. Far fewer studies have evaluated whether or not associations encountered just once prior to testing might also be accessed and influence behavior. Here, eye movements were used to examine whether or not memory for studied relationships is evident following the presentation of subliminal cues. Participants assigned to experimental or control groups studied scene-face pairs and test trials evaluated implicit and explicit memory for these pairs. Each test trial began with a subliminal scene cue, followed by three visible studied faces. For experimental group participants, one face was the studied associate of the scene (implicit test); for controls none were a match. Subsequently, the display containing a match was presented to both groups, but now it was preceded by a visible scene cue (explicit test). Eye movements were recorded and recognition memory responses were made. Participants in the experimental group looked disproportionately at matching faces on implicit test trials and participants from both groups looked disproportionately at matching faces on explicit test trials, even when that face had not been successfully identified as the associate. Critically, implicit memory-based viewing effects seemed not to depend on residual awareness of subliminal scene cues, as subjective and objective measures indicated that scenes were successfully masked from view. The reported outcomes indicate that memory for studied relationships can be expressed in eye movement behavior without awareness.

pone.0141677.g004: Implicit Memory-Based Viewing Effects.A) Proportion of total viewing time directed to faces of interest collapsed across the duration of the entire test trial for the experimental group (top) and the control group (bottom). More time was spent looking at faces that happened to have been selected, but there were no effects of memory in viewing patterns. B) Proportion of total viewing time direct to faces of interest broken down into 250ms time bins starting with 3-face display onset. Faces that happened to have been selected were prioritized, but effects of memory on the viewing behavior of experimental group participants (top) are also evident; the same effects are absent from control data (bottom). Error bars indicate standard errors of the mean.

Mentions:
Global Measures: There were no differences in the proportion of total viewing time directed to critical faces (selected or not) relative to corresponding matched comparison faces for either group (Experimental Group: t’s(18) ≤ .31, p’s ≥ .76; Control Group: t’s(19) ≤ .80, p’s ≥ .44). A between-groups repeated measures ANOVA with the factors face type (critical face, comparison foil face) and selection history (selected, not selected) indicated that more time was spent viewing faces that happened to have been selected vs. not (F(1,37) = 101.24, p < .001), but none of the remaining main effects or interactions were statistically reliable (all F’s ≤ .52, p’s ≥ .48; see Fig 4A). This outcome was not unexpected, as previous work indicates that memory-based viewing effects may be especially robust soon after test display onset, and can be obscured when data are collapsed across the entire duration of a test display (cf. Hannula et al., 2007). Time-course measures, described next, were used to determine whether or not there were differences early in viewing that distinguished studied associates from corresponding matched comparison faces.

pone.0141677.g004: Implicit Memory-Based Viewing Effects.A) Proportion of total viewing time directed to faces of interest collapsed across the duration of the entire test trial for the experimental group (top) and the control group (bottom). More time was spent looking at faces that happened to have been selected, but there were no effects of memory in viewing patterns. B) Proportion of total viewing time direct to faces of interest broken down into 250ms time bins starting with 3-face display onset. Faces that happened to have been selected were prioritized, but effects of memory on the viewing behavior of experimental group participants (top) are also evident; the same effects are absent from control data (bottom). Error bars indicate standard errors of the mean.

Mentions:
Global Measures: There were no differences in the proportion of total viewing time directed to critical faces (selected or not) relative to corresponding matched comparison faces for either group (Experimental Group: t’s(18) ≤ .31, p’s ≥ .76; Control Group: t’s(19) ≤ .80, p’s ≥ .44). A between-groups repeated measures ANOVA with the factors face type (critical face, comparison foil face) and selection history (selected, not selected) indicated that more time was spent viewing faces that happened to have been selected vs. not (F(1,37) = 101.24, p < .001), but none of the remaining main effects or interactions were statistically reliable (all F’s ≤ .52, p’s ≥ .48; see Fig 4A). This outcome was not unexpected, as previous work indicates that memory-based viewing effects may be especially robust soon after test display onset, and can be obscured when data are collapsed across the entire duration of a test display (cf. Hannula et al., 2007). Time-course measures, described next, were used to determine whether or not there were differences early in viewing that distinguished studied associates from corresponding matched comparison faces.

Bottom Line:
While it is generally agreed that perception can occur without awareness, there continues to be debate about the type of representational content that is accessible when awareness is minimized or eliminated.Eye movements were recorded and recognition memory responses were made.The reported outcomes indicate that memory for studied relationships can be expressed in eye movement behavior without awareness.

Affiliation:
Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States of America.

ABSTRACTWhile it is generally agreed that perception can occur without awareness, there continues to be debate about the type of representational content that is accessible when awareness is minimized or eliminated. Most investigations that have addressed this issue evaluate access to well-learned representations. Far fewer studies have evaluated whether or not associations encountered just once prior to testing might also be accessed and influence behavior. Here, eye movements were used to examine whether or not memory for studied relationships is evident following the presentation of subliminal cues. Participants assigned to experimental or control groups studied scene-face pairs and test trials evaluated implicit and explicit memory for these pairs. Each test trial began with a subliminal scene cue, followed by three visible studied faces. For experimental group participants, one face was the studied associate of the scene (implicit test); for controls none were a match. Subsequently, the display containing a match was presented to both groups, but now it was preceded by a visible scene cue (explicit test). Eye movements were recorded and recognition memory responses were made. Participants in the experimental group looked disproportionately at matching faces on implicit test trials and participants from both groups looked disproportionately at matching faces on explicit test trials, even when that face had not been successfully identified as the associate. Critically, implicit memory-based viewing effects seemed not to depend on residual awareness of subliminal scene cues, as subjective and objective measures indicated that scenes were successfully masked from view. The reported outcomes indicate that memory for studied relationships can be expressed in eye movement behavior without awareness.